The present invention relates to a network system having a line switching function, and in particular, to a network system in which at a failure of a communication line, the failed line can be changed over to a backup line through a remote centralized control conducted by a network control center.
With advances of networking, a system has been generally employed in which computers installed at remote locations are linked with communication lines to execute information processing. In this situation, reliability of the network system becomes quite important, and as a measure to obtain higher reliability, constituent components of the system are configured in a duplicated fashion. For a line failure, the line is replaced with a backup line. JP-A Nos. 58-44839 and 63-193653 disclose a change-over of a failed line to a backup line at an occurrence of a communication line failure. In general, the change-over of the failed line to the backup line is conducted by use of switches of line switching units installed at respective points of the network. According to the prior art technology above, the change-over operation is achieved in at least one of the duplicated line switching units. Consequently, in a network system comprising many line switching units, many maintenance engineers are required to stay as resident operators at the respective locations of the line switching units.